In assembly and manufacturing lines, oftentimes there are many machines working simultaneously and production units moving down the line between the machines. Different machines perform different tasks and at different stations, production units may spend more or less time. In a preferred situation, all machines at all stations are operational and production units are moving smoothly in the buffers between stations.
In actual production, not all machines are necessarily operational and production units are not typically moving smoothly in the buffers betweens stations. There may be different reasons that not all machines are operational. For example, a machine may be idle because it is in a starved condition, that is, because there are no production units available at that particular station due to a lack of production units in the buffer feeding into that machine. A machine also may be idle because a personnel shift change is taking place, from, for example, the morning shift to the evening shift. A machine also may be idle if the operator is on a break.
A machine may be idle because the machine may be subject to a maintenance window. That is, it may be idle when maintenance is performed or waiting to be performed on a machine. The maintenance may be done according to a schedule, or there may be an immediate need due to machine malfunction. In this situation, the station operator may be made idle and may take an unscheduled break. The buffer feeding into the station may become full, causing a blocked condition in the machine immediately upstream, while the buffer fed by the station may become empty, causing a starved condition in the machine immediately downstream. This may lead station operators down the line to take unscheduled breaks. In any of these situations, time is not being efficiently utilized and therefore the production process is not cost effective. The common approach to avoiding production losses due to maintenance windows is to schedule maintenance during unscheduled overtime.
In a large production environment such as those used to manufacture automobiles, the production line may include 25 miles of conveyor. The plant itself may be three million square feet. Any increase in production timing precision is desirable for better resource allocation. Accordingly, processes that keep the line moving are advantageous.
For monitoring lines, a monitoring display may be provided in a central location that shows zones of the production that may comprise a plurality of production stations. The display shows the status of the production zones at a particular current time. The number of production units in a buffer at that current time may be shown. From that number, a maintenance operator can determine if a maintenance window on a station down the line is open.
In the current system if there are few or no units in the buffer, the operator views the monitoring display and then can roughly estimate the amount of time maintenance personnel may have to service the machine or machines down the line from the buffer. In the short term, if too much time is allocated or taken for maintenance personnel to service a machine, the buffer before the station may become blocked. Once the serviced machine is back online, the line may take more time than desirable to return to smooth operation.
In another situation relating to the longer term, it is not uncommon for service or trade personnel such as electricians to inadvertently modify parameters which may slow down cycle times. Over a period of time the zone may slow down, even if only by a second or two. However, the cumulative effect over the long term, once noticed, may have a substantial impact on overall production.
As mentioned above, the management is charged with the responsibility of watching display monitors showing rectangular indicators of different colors representing various production zones and their current statuses. According to those display monitors, the maintenance operator generally makes ad hoc decisions as to where and when to allocate maintenance personnel. Routine maintenance occurs when the opportunity arises according to the display monitors, instead of by adherence to a firm schedule of maintenance. The machines and their longevity would benefit from timely scheduled maintenance.
It would be preferable to predict opportunities that maintenance personnel may have to perform their particular maintenance duties. It would further be preferable to relieve the maintenance operator of the tedious task of monitoring the display monitors for short-lived opportunities for machinery maintenance. It would also be preferable to substantially ensure that scheduled maintenance activities occur in a timely manner. Finally, it would be advantageous to utilize maintenance personnel more fully by scheduling their work according to predicted maintenance opportunities and avoiding unscheduled overtime.